std: replace LazyBox with OnceBox

This PR replaces the `LazyBox` wrapper used to allocate the pthread primitives with `OnceBox`, which has a more familiar API mirroring that of `OnceLock`. This cleans up the code in preparation for larger changes like #128184 (from which this PR was split) and allows some neat optimizations, like avoid an acquire-load of the allocation pointer in `Mutex::unlock`, where the initialization of the allocation must have already been observed.

Additionally, I've gotten rid of the TEEOS `Condvar` code, it's just a duplicate of the pthread one anyway and I didn't want to repeat myself.

Author: joboet

library/std/src/sys/sync/condvar/mod.rs

@@ -12,7 +12,10 @@ cfg_if::cfg_if! {
     ))] {
         mod futex;
         pub use futex::Condvar;
-    } else if #[cfg(target_family = "unix")] {
+    } else if #[cfg(any(
+        target_family = "unix",
+        target_os = "teeos",
+    ))] {
         mod pthread;
         pub use pthread::Condvar;
     } else if #[cfg(all(target_os = "windows", target_vendor = "win7"))] {
@@ -24,9 +27,6 @@ cfg_if::cfg_if! {
     } else if #[cfg(target_os = "solid_asp3")] {
         mod itron;
         pub use itron::Condvar;
-    } else if #[cfg(target_os = "teeos")] {
-        mod teeos;
-        pub use teeos::Condvar;
     } else if #[cfg(target_os = "xous")] {
         mod xous;
         pub use xous::Condvar;

library/std/src/sys/sync/condvar/pthread.rs

@@ -2,31 +2,25 @@ use crate::cell::UnsafeCell;
 use crate::ptr;
 use crate::sync::atomic::AtomicPtr;
 use crate::sync::atomic::Ordering::Relaxed;
-use crate::sys::sync::{Mutex, mutex};
+use crate::sys::sync::{Mutex, OnceBox};
 #[cfg(not(target_os = "nto"))]
 use crate::sys::time::TIMESPEC_MAX;
 #[cfg(target_os = "nto")]
 use crate::sys::time::TIMESPEC_MAX_CAPPED;
-use crate::sys_common::lazy_box::{LazyBox, LazyInit};
 use crate::time::Duration;
 
 struct AllocatedCondvar(UnsafeCell<libc::pthread_cond_t>);
 
 pub struct Condvar {
-    inner: LazyBox<AllocatedCondvar>,
+    inner: OnceBox<AllocatedCondvar>,
     mutex: AtomicPtr<libc::pthread_mutex_t>,
 }
 
-#[inline]
-fn raw(c: &Condvar) -> *mut libc::pthread_cond_t {
-    c.inner.0.get()
-}
-
 unsafe impl Send for AllocatedCondvar {}
 unsafe impl Sync for AllocatedCondvar {}
 
-impl LazyInit for AllocatedCondvar {
-    fn init() -> Box<Self> {
+impl AllocatedCondvar {
+    fn new() -> Box<Self> {
         let condvar = Box::new(AllocatedCondvar(UnsafeCell::new(libc::PTHREAD_COND_INITIALIZER)));
 
         cfg_if::cfg_if! {
@@ -37,7 +31,7 @@ impl LazyInit for AllocatedCondvar {
                 target_vendor = "apple",
             ))] {
                 // `pthread_condattr_setclock` is unfortunately not supported on these platforms.
-            } else if #[cfg(any(target_os = "espidf", target_os = "horizon"))] {
+            } else if #[cfg(any(target_os = "espidf", target_os = "horizon", target_os = "teeos"))] {
                 // NOTE: ESP-IDF's PTHREAD_COND_INITIALIZER support is not released yet
                 // So on that platform, init() should always be called
                 // Moreover, that platform does not have pthread_condattr_setclock support,
@@ -82,7 +76,11 @@ impl Drop for AllocatedCondvar {
 
 impl Condvar {
     pub const fn new() -> Condvar {
-        Condvar { inner: LazyBox::new(), mutex: AtomicPtr::new(ptr::null_mut()) }
+        Condvar { inner: OnceBox::new(), mutex: AtomicPtr::new(ptr::null_mut()) }
+    }
+
+    fn get(&self) -> *mut libc::pthread_cond_t {
+        self.inner.get_or_init(AllocatedCondvar::new).0.get()
     }
 
     #[inline]
@@ -98,21 +96,21 @@ impl Condvar {
 
     #[inline]
     pub fn notify_one(&self) {
-        let r = unsafe { libc::pthread_cond_signal(raw(self)) };
+        let r = unsafe { libc::pthread_cond_signal(self.get()) };
         debug_assert_eq!(r, 0);
     }
 
     #[inline]
     pub fn notify_all(&self) {
-        let r = unsafe { libc::pthread_cond_broadcast(raw(self)) };
+        let r = unsafe { libc::pthread_cond_broadcast(self.get()) };
         debug_assert_eq!(r, 0);
     }
 
     #[inline]
     pub unsafe fn wait(&self, mutex: &Mutex) {
-        let mutex = mutex::raw(mutex);
+        let mutex = mutex.get_assert_locked();
         self.verify(mutex);
-        let r = libc::pthread_cond_wait(raw(self), mutex);
+        let r = libc::pthread_cond_wait(self.get(), mutex);
         debug_assert_eq!(r, 0);
     }
 
@@ -129,7 +127,7 @@ impl Condvar {
     pub unsafe fn wait_timeout(&self, mutex: &Mutex, dur: Duration) -> bool {
         use crate::sys::time::Timespec;
 
-        let mutex = mutex::raw(mutex);
+        let mutex = mutex.get_assert_locked();
         self.verify(mutex);
 
         #[cfg(not(target_os = "nto"))]
@@ -144,7 +142,7 @@ impl Condvar {
             .and_then(|t| t.to_timespec_capped())
             .unwrap_or(TIMESPEC_MAX_CAPPED);
 
-        let r = libc::pthread_cond_timedwait(raw(self), mutex, &timeout);
+        let r = libc::pthread_cond_timedwait(self.get(), mutex, &timeout);
         assert!(r == libc::ETIMEDOUT || r == 0);
         r == 0
     }
@@ -162,7 +160,7 @@ impl Condvar {
         use crate::sys::time::SystemTime;
         use crate::time::Instant;
 
-        let mutex = mutex::raw(mutex);
+        let mutex = mutex.get_assert_locked();
         self.verify(mutex);
 
         // OSX implementation of `pthread_cond_timedwait` is buggy
@@ -188,7 +186,7 @@ impl Condvar {
             .and_then(|t| t.to_timespec())
             .unwrap_or(TIMESPEC_MAX);
 
-        let r = libc::pthread_cond_timedwait(raw(self), mutex, &timeout);
+        let r = libc::pthread_cond_timedwait(self.get(), mutex, &timeout);
         debug_assert!(r == libc::ETIMEDOUT || r == 0);
 
         // ETIMEDOUT is not a totally reliable method of determining timeout due

library/std/src/sys/sync/condvar/sgx.rs

@@ -1,44 +1,39 @@
 use crate::sys::pal::waitqueue::{SpinMutex, WaitQueue, WaitVariable};
-use crate::sys::sync::Mutex;
-use crate::sys_common::lazy_box::{LazyBox, LazyInit};
+use crate::sys::sync::{Mutex, OnceBox};
 use crate::time::Duration;
 
-/// FIXME: `UnsafeList` is not movable.
-struct AllocatedCondvar(SpinMutex<WaitVariable<()>>);
-
 pub struct Condvar {
-    inner: LazyBox<AllocatedCondvar>,
-}
-
-impl LazyInit for AllocatedCondvar {
-    fn init() -> Box<Self> {
-        Box::new(AllocatedCondvar(SpinMutex::new(WaitVariable::new(()))))
-    }
+    // FIXME: `UnsafeList` is not movable.
+    inner: OnceBox<SpinMutex<WaitVariable<()>>>,
 }
 
 impl Condvar {
     pub const fn new() -> Condvar {
-        Condvar { inner: LazyBox::new() }
+        Condvar { inner: OnceBox::new() }
+    }
+
+    fn get(&self) -> &SpinMutex<WaitVariable<()>> {
+        self.inner.get_or_init(|| Box::new(SpinMutex::new(WaitVariable::new(()))))
     }
 
     #[inline]
     pub fn notify_one(&self) {
-        let _ = WaitQueue::notify_one(self.inner.0.lock());
+        let _ = WaitQueue::notify_one(self.get().lock());
     }
 
     #[inline]
     pub fn notify_all(&self) {
-        let _ = WaitQueue::notify_all(self.inner.0.lock());
+        let _ = WaitQueue::notify_all(self.get().lock());
     }
 
     pub unsafe fn wait(&self, mutex: &Mutex) {
-        let guard = self.inner.0.lock();
+        let guard = self.get().lock();
         WaitQueue::wait(guard, || unsafe { mutex.unlock() });
         mutex.lock()
     }
 
     pub unsafe fn wait_timeout(&self, mutex: &Mutex, dur: Duration) -> bool {
-        let success = WaitQueue::wait_timeout(&self.inner.0, dur, || unsafe { mutex.unlock() });
+        let success = WaitQueue::wait_timeout(self.get(), dur, || unsafe { mutex.unlock() });
         mutex.lock();
         success
     }

library/std/src/sys/sync/condvar/teeos.rs

@@ -1,11 +1,14 @@
 mod condvar;
 mod mutex;
 mod once;
+mod once_box;
 mod rwlock;
 mod thread_parking;
 
 pub use condvar::Condvar;
 pub use mutex::Mutex;
 pub use once::{Once, OnceState};
+#[allow(unused)] // Only used on some platforms.
+use once_box::OnceBox;
 pub use rwlock::RwLock;
 pub use thread_parking::Parker;

library/std/src/sys/sync/mod.rs

@@ -19,7 +19,7 @@ cfg_if::cfg_if! {
         target_os = "teeos",
     ))] {
         mod pthread;
-        pub use pthread::{Mutex, raw};
+        pub use pthread::Mutex;
     } else if #[cfg(all(target_os = "windows", target_vendor = "win7"))] {
         mod windows7;
         pub use windows7::{Mutex, raw};